1. Field of the Invention
The present invention generally relates to a method of controlling travel of construction heavy equipment with electronic joysticks, with which a driver can control the travel of the construction heavy equipment in a comfort sitting posture.
The present invention specifically relates to a method of controlling travel of construction heavy equipment with electronic joysticks, capable of selectively driving a working unit and a traveling unit by using the electronic joysticks for the working unit such as a boom, an arm or so forth.
2. Description of the Related Art
In general, construction heavy equipment such as an excavator makes use of an acceleration pedal or a travel lever connected with the acceleration pedal which is for performing travel operation, and a manipulation lever, such as a joystick, for a working unit such as a boom, an arm, a bucket, a swing unit or so forth.
Currently, an electronic joystick is widely used as the manipulation lever, wherein the joystick outputs a signal in proportion to a quantity of manipulation caused by a driver or operator. The signal outputted from the joystick may be an analog voltage signal, a PWM (Pulse Width Modulation) signal, a communication signal, etc.
Various working units including the swing unit and the traveling unit are driven by a hydraulic fluid supplied from a hydraulic pump operated by an engine. A control unit controls a direction and a flow rate of a hydraulic fluid supplied to the working units by controlling various control valves according to the manipulation quantity of the manipulation lever, so that the working units and the traveling unit are driven.
In order to make the heavy equipment travel, the driver has either to press the acceleration pedal with his/her foot or to manipulate the travel lever connected with the acceleration pedal with his/her hand. When the driver manipulates the joystick for the working unit, he/she can work in a state where he/she assumes a comfortable posture on the driver's seat. However, when the travel lever installed a little apart in front of the driver's seat is manipulated, the driver must manipulate the travel lever in a state where he/she leans forward in the driver's seat to a certain degree.
During long-distance traveling, the driver must step on the acceleration pedal under continuous application of a constant force. For this reason, the travel lever is used instead of the acceleration pedal. In this case, the driver must lean forward in the driver's seat for a long time. Thus, the driver easily feels tired.
According to a prior art for overcoming these drawbacks, a manipulation lever for a traveling unit has been installed around a joystick for a working unit. With this configuration, the manipulation lever must be installed separately from a hydraulic line, so that the configuration becomes complicated and production costs are increased.
According to another prior art, a control valve has been installed on a pilot signal line connected to a joystick of a working unit. When the control valve is switched, a pilot signal pressure of the joystick being supplied to the working unit is adapted to be supplied to a traveling unit, so that any one of the working unit and the traveling unit is selectively driven by using the joystick.
However, according to these prior arts, a configuration of a hydraulic circuit becomes complicated, and thereby production costs are increased. Further, there is a limitation that this configuration can not be applied to the state-of-the-art heavy equipment where all the units of the heavy equipment are controlled by electrical and electronic signals from an electronic proportional valve etc.